Method and system for comparing free-form geometries using high density point data models

Abstract

A method is provided for verifying the accuracy of a part geometry with respect to a master geometry. The method begins with the step of providing a computer workstation including a computer and an output device attached to the computer. The method also includes the steps of generating a master HDPDM describing the geometry of the master and generating a part HDPDM describing the geometry of the part. The master HDPDM includes a plurality of points. The method further includes the step of aligning the master HDPDM and the part HDPDM within a coordinate frame. The method continues with the step of computing the distance from each point of the master HDPDM to the surface described by the part HDPDM to obtain signed distance data. The method concludes with the step of displaying an image on the output device based on the signed distance data. The image represents the non-conformance between the master and the part and is used to verify the accuracy of the geometry of the part with respect to the geometry of the master.

We claim: 
     
       1. A method for verifying the accuracy of a geometry of a part with respect to the geometry of a master, the method comprising: providing a computer workstation including a computer and an output device attached to the computer;   generating a master HDPDM having a plurality of points, the master HDPDM describing the geometry of the master;   scanning a surface of a part to generate scanned part   converting the scanned part signals to corresponding electrical part signals;   generating a part HDPDM based on the electrical part signals, the part HDPDM having a plurality of points describing the geometry of the part;   aligning the master HDPDM and part HDPDM within a coordinate frame;   computing the distance from each point of the master HDPDM to the surface described by the part HDPDM to obtain signed distance data; and   outputing an image on the output device based on the signed distance data, the image including a plurality of pixels representing the geometry of the master, each pixel being coded to indicate non-conformance between the master and the part based on the step computing to verify the accuracy of the geometry of the part with respect to the geometry of the master.   
     
     
       2. The method of claim 1 wherein the step of generating the master HDPDM includes: tessellating a CAD model to produce tesselated object data; and   regriding the tesselated object data to obtain the master HDPDM.   
     
     
       3. The method of claim 1 wherein the step of generating a part HDPDM includes: tessellating a CAD model to produce tesselated object data; and   regriding the tesselated object data to obtain the part HDPDM.   
     
     
       4. The method of claim 1 wherein the step of generating the master HDPDM includes: selecting discrete values along a first and second mutually exclusive orthogonal axis; and   calculating discrete values along a third mutually exclusive orthogonal axis based on a master math model to obtain the master HDPDM.   
     
     
       5. The method of claim 1 wherein the step of generating the part HDPDM includes: selecting discrete values along a first and second mutually exclusive orthogonal axis; and   calculating discrete values along a third mutually exclusive orthogonal axis based on a part math model to obtain the part HDPDM.   
     
     
       6. The method of claim 1 wherein the step of generating the master HDPDM includes: scanning the master at discrete values of X and Y to obtain scan data; and   processing the scan data to obtain the master HDPDM.   
     
     
       7. The method of claim 1 wherein the step of generating the part HDPDM includes: scanning the part at discrete values of X and Y to obtain scan data; and   processing the scan data to obtain the part HDPDM.   
     
     
       8. The method of claim 1 wherein the step of aligning includes: providing a first set of reference data identifying reference features of the first object;   providing a second set of reference data identifying reference features of the second object;   computing a transformation equation based on the first and second sets of reference data; and   updating the part HDPDM based on the transformation equation, wherein the updated part HDPDM is utilized in the step of computing the distance.   
     
     
       9. The method of claim 1 wherein the step of displaying includes: selecting a plurality of ranges of non-conformity based on the signed distance data;   selecting a plurality of colors to be associated with the plurality of ranges; and   displaying an image using the plurality of colors, each color indicating non-conformity between the first and second objects within its associated range.   
     
     
       10. A system for verifying the accuracy of a geometry of a part with respect to the geometry of a master, the system comprising: a computer workstation including a computer and an output device attached to the computer;   means for generating a master HDPDM having a plurality of points, the master HDPDM describing the geometry of the master;   means for scanning a surface of a part to generate scanned part signals;   means for converting the scanned part signals to corresponding electrical part signals;   means for generating a part HDPDM based on the electrical part signals, the part HDPDM having a plurality of points describing the geometry of the part;   means for aligning the master HDPDM and part HDPDM within a coordinate frame;   means for computing the distance from each point of the master HDPDM to the surface described by the part HDPDM to obtain signed distance data; and   means for outputting an image on the output device based on the signed distance data, the image including a plurality of pixels representing the geometry of the master, each pixel being coded to indicate non-conformance between the master and the part to verify the accuracy of the geometry of the part with respect to the geometry of the master.   
     
     
       11. The system of claim 10 wherein the means for generating the master HDPDM includes: means for tessellating a CAD model to produce tesselated object data; and   means for regriding the tesselated object data to obtain the master HDPDH.   
     
     
       12. The system of claim 10 wherein the means for generating a part HDPDH includes: means for tessellating a CAD model to produce tesselated object data; and   means for regriding the tesselated object data to obtain the part HDPDM.   
     
     
       13. The system of claim 10 wherein the means for generating the master HDPDM includes: means for selecting discrete values along a first and second mutually exclusive orthogonal axis; and   means for calculating discrete values along a third mutually exclusive orthogonal axis based on a master math model to obtain the master HDPDM.   
     
     
       14. The system of claim 10 wherein the means for generating the part HDPDM includes: means for selecting discrete values along a first and second mutually exclusive orthogonal axis; and   means for calculating discrete values along a third mutually exclusive orthogonal axis based on a part math model to obtain the part HDPDM.   
     
     
       15. The system of claim 10 wherein the means for generating the master HDPDM includes: means for scanning the master at discrete values of X and Y to obtain scan data; and   means for processing the scan data to obtain the master HDPDM.   
     
     
       16. The system of claim 10 wherein the means for generating the part HDPDM includes: means for scanning the part at discrete values of X and Y to obtain scan data; and   means for processing the scan data to obtain the part HDPDM.   
     
     
       17. The system of claim 10 wherein the means for aligning includes: means for providing a first set of reference data identifying reference features of the first object;   means for providing a second set of reference data identifying reference features of the second object;   means for computing a transformation equation based on the first and second sets of reference data; and   means for updating the part HDPDM based on the transformation equation, wherein the updated part HDPDM is utilised in the step of computing the distance.   
     
     
       18. The system of claim 10 wherein the means for displaying includes: means for selecting a plurality of ranges of non-conformity based on the signed distance data;   means for selecting a plurality of colors to be associated with the plurality of ranges; and   means for displaying an image using the plurality of colors, each color indicating non-conformity between the first and second objects within its associated range.